The external-resource key(s) a GitHub payload concerns — matched against a
subscription's externalResourceId. A repo event yields github:<full_name>;
an issue / PR event ALSO yields github:<full_name>#<number>, so a
subscription may watch the whole repo OR one issue/PR. Nothing usable ⇒ [].
The external-resource key(s) a GitHub payload concerns — matched against a subscription's
externalResourceId. A repo event yieldsgithub:<full_name>; an issue / PR event ALSO yieldsgithub:<full_name>#<number>, so a subscription may watch the whole repo OR one issue/PR. Nothing usable ⇒ [].